Along with the prosperity in portable electronic products, the notebook computer has a trend of light-weight and becomes popular with users in the youth generation. Besides the appearance, the practical function of the notebook computer is also one of key factors to determine a final purchase of a notebook computer. One of various options in a typical notebook computer is the index device for controlling the cursor on the screen. Options of the index devices include mice, track balls, joy sticks, touch pads, push pillars and so on. In particular, the touch pad whose operation involve only movements of user's finger on the touch pad and some key striking is definite a suitable device to be built in the notebook computer.
Referring to FIG. 1a, a perspective view of a conventional notebook having a touch pad is shown. The notebook 1 (i.e. briefing of “notebook computer”) includes an upper housing 101, a lower housing 102, a display screen 11, an operation panel 12 and a touch pad assembly 13. The display screen 11 and the operation panel 12 are located respectively on the upper housing 101 and the lower housing 102. The touch pad assembly 13 is located on the lower housing 102 next to the operation panel 12.
Referring to FIG. 1b, a cross sectional view of the touch pad 13 along line AA′ of FIG. 1a is shown. The touch pad assembly 13 includes a touch pad 131, a fixed frame 132 and a printed circuit board 133. The fixed frame 132 is transversely (in the paper view) structured to the lower housing 102. The touch pad 131 is then mainly supported by the fixed frame 132 in the middle. The printed circuit board 133 sets right under the touch pad 131 and have two switches 134 on two sides with respect to the fixed frame 132. By depressing the touch pad 131 properly to trigger the switch 134, a predetermined electrical signal can be generated and forwarded to the printed circuit board 133 so as to initiate a preset action of the notebook computer.
For the middle-located fixed axle is a solid support with respect to the touch pad, so a depression close enough to the fixed axle would be quite possible to cause no substantial deflection to the touch pad so that an expected electrical action at the switch under the touch pad might be missed. Further, for the fixed axle halves the elastic touch pad, no seesaw-like motion about the fixed axle can be provided to avoid a possible double hitting at both halves of the touch pad, which definitely leads to a wrong or invalid switch action.